1. Field of the Invention
The present invention relates to waveguide structures for microwave signal transmission and, more particularly, to junction elements for microwave waveguide multiplexers.
2. Background Art
A microwave waveguide multiplexer is a device that either combines or separates microwave signals of different frequencies. A typical waveguide multiplexer is fabricated by joining a filter to a waveguide manifold. The filter is composed of iris coupled waveguide cavity resonators and the waveguide manifold is a length of rectangular waveguide with one end having a metal shorting plate and the other end connected to a transmit or receive port. In the art, junctions are usually formed either by a direct connection of the filter to the broad or narrow wall of the manifold waveguide or by an additional intermediate length of rectangular waveguide connected perpendicular to the manifold and forming a T-junction.
A conventional method of controlling a junction response is to vary the T-junction distance between the filter and the manifold by expensive cut-and-try methods. This requires the development of a breadboard for each design to ensure that the specifications can be met. Also the T-junction separation distance needed can be very large, resulting in a narrow operating frequency band. Since larger microwave devices have a narrower frequency band over which they operate successfully, a junction with a step as provided by the present invention will achieve a wider bandwidth of operation than a T-junction.